Such metering pumps comprise, in general, a delivery plunger, which can be moved to and fro for delivering the liquid fuel and is accommodated and guided for this purpose, for example, in a guide sleeve. Due to its reciprocating movement, the plunger dips more or less deeply into the guide sleeve depending on its movement cycle. The liquid fuel is ejected in this manner from a pump ejection chamber, which is also defined by an inner surface of the guide sleeve, namely, when the delivery plunger is being moved in the direction in which the pump ejection chamber volume is minimized, or fuel can be taken up in the chamber, namely, when the delivery plunger is being moved in the direction in which the pump ejection chamber volume is maximized.
This guide sleeve is carried, in general, firmly in a carrier element, which may be part of a housing of the metering pump or in such a housing. To make it possible to guide the liquid fuel in the direction of the pump ejection chamber, a circumferential distance is present between an outer surface of the guide sleeve and the carrier element, which carries the guide sleeve per se, so that an annular flow space is formed. This leads in the direction of the pump ejection chamber. In another length area, the guide sleeve is in contact with the carrier element essentially over the entire circumferential area, so that stable mounting of the guide sleeve is ensured by press fit, on the hand, and, on the other hand, the annular channel area is axially defined and it is ensured that no liquid fuel can escape in the transition between the carrier element and the guide sleeve. To achieve the stable mounting of the guide sleeve, the latter must be made, in general, of a metallic material, so that this mounting is brought about in a comparatively short length area by the contact between the guide sleeve and the carrier element, while the annular intermediate space, in which there is no contact between the guide sleeve and the carrier element, is then formed in a longer section. This is also due to the fact that such guide sleeves are brought, in general, to the desired dimensions by a turning operation, so that, in principle, a rotationally symmetrical outer surface is obtained, as a consequence of which the load-bearing contact with the carrier element is present only in a predetermined length area.